1. Technical Field
The present invention relates to a reflective optical sensor and an image forming apparatus.
2. Description of Related Art
An image forming apparatus forming color images with different color toners have been widely implemented such as an analog or digital color copier, a printer, a facsimile machine or a multi-function printer (MFP).
For example, Japanese Laid-open Patent Application Publication No. 5-113739 (Reference 1), Japanese Patent No. 4632820 (Reference 2), and Japanese Laid-open Patent Application Publication No. 2014-56018 (Reference 3) disclose such an image forming apparatus which writes an electrostatic latent image on the surface of an image bearer, visualizes the electrostatic latent image by attaching a developer including toner, transfers the image onto a recording medium as paper, and fixes the image onto a fixing element such as a fixing belt.
A repetition of image fixation may cause a defect such as scratches on the surface of the fixing element, which results in adversely affecting image quality. To prevent an adverse effect on image quality, the image forming apparatus in Reference 1 includes photosensors which receive light emitted from a light source and reflected by the surface of a fixing roller, to detect a defect on the surface of the fixing roller on the basis of the intensity of the received reflected light.
Further, the image forming apparatus in Reference 2 includes a detector such as a photosensor which senses a scratch and the periphery of the scratch on the fixing belt, so as to attach a larger amount of developer onto a scratch portion and make the scratch less conspicuous on an image. Reference 3 discloses a reflective optical sensor having a number of light emitters and a light receiving element to illuminate the surface of the fixing belt with light spots from the light emitting elements and receive light reflected by the fixing belt at the light receiving element to detect a surface condition of the fixing belt.
However, a moving element as the fixing belt may meander and flop, causing a variation in detected values of the photosensor and affecting the accuracy at which the surface condition of the moving element is detected.